The invention relates to a plant for the processing of residue from a thermal waste disposal plant. The residue has a combustible carbon-containing constituent and a non-combustible constituent, and the plant has a first device for the substantial separation of the combustible constituent from the non-combustible constituent.
For ecological and economic reasons, in thermal waste disposal plants, particularly in pyrolysis plants, the residue occurring during thermal treatment is sorted and, if possible, reused. The aim, in this case, is to separate the residue into the carbon-containing combustible constituent and into the non-combustible constituent.
Published, European Patent Application EP 0 302 310 A and the company publication xe2x80x9cDie Schwel-Brenn-Anlage, eine Verfahrensbeschreibungxe2x80x9d [xe2x80x9cThe Low-Temperature Carbonization Incineration Plant, A Process Descriptionxe2x80x9d], published by Siemens AG, Berlin and Munich, 1996, disclose, as a pyrolysis plant, a so-called low-temperature carbonization incineration plant, in which essentially a two-stage method is carried out. In the first stage, the waste delivered is introduced into a low-temperature carbonization drum (pyrolysis reactor) and is carbonized at low temperature (pyrolyzed). During pyrolysis, low-temperature carbonization gas and pyrolysis residue are obtained in the low-temperature carbonization drum. The low-temperature carbonization gas is burnt, together with combustible fragments of the pyrolysis residue, in a high-temperature combustion chamber at temperatures of approximately 1200xc2x0 C. The exhaust gases occurring at the same time are subsequently purified.
The pyrolysis residue also has, in addition to the combustible fragments, a large proportion of non-combustible fragments. The non-combustible constituents are composed essentially of an inert fraction, which contains glass, stone, and ceramic fragments, and of a metal fraction. The latter can be divided into a non-ferrous fraction and a ferrous fraction. The non-combustible constituents are sorted out as residues and supplied for re-utilization. For ecological reasons, which are also reflected in statutory regulations, the proportion of carbon in the non-combustible constituents should be as low as possible.
Published, European Patent Application EP 0 144 535 A2 discloses a method for the thermal treatment of waste with re-utilization of the residue obtained, in which, in a first screening, a coarse fraction is separated from the pyrolysis residue and the remaining smaller fraction is subjected to a second screening. The two fractions obtained during the second screening are each subjected to air separation, in order to separate a low-carbon heavy fraction from a carbon-rich light fraction. The carbon-rich light fraction is supplied for energy utilization and the low-carbon fraction is intended for dumping or, for example, for road construction.
A method for the processing of light shredder refuse, which occurs during the comminution of metal-containing residues, for example when cars are being crushed, is described in Published, Non-Prosecuted German Patent Application DE 44 26 503 A1. During this processing, after screening there is provision for the separation of pellets, this being followed by classifying in order to separate a very light plastic fraction. The light fraction separated in this case is added to a fuel fraction.
The problem of the known methods is that the separated non-combustible constituent of the pyrolysis residue, despite being classified, has a considerable proportion of carbon-containing combustible constituents.
It is accordingly an object of the invention to provide a plant for the processing of residue from a thermal waste disposal plant that overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which the carbon-containing solid fragments are separated essentially completely and reliably in an operation which, in particular, is continuous.
With the foregoing and other objects in view there is provided, in accordance with the invention, a plant for processing a residue from a thermal waste disposal plant, the residue having a combustible carbon-containing constituent and a non-combustible constituent. The plant contains a first device receiving the residue and substantially separating the combustible carbon-containing constituent from the non-combustible constituent. A second device is disposed downstream from the first device and separates the non-combustible constituent into a small fragment fraction and a large fragment fraction. A third device for dividing up the small fragment fraction is disposed downstream of the second device. The third device has a drum with drivers for separating wire-like constituents from the small fragment fraction, a screening device for separating elongated constituents from the small fragment fraction, and a heavy-fragment separator for separating a carbon-containing light fraction still present in the small fragment fraction.
In the plant, the non-combustible constituent is initially essentially separated from the carbon-containing combustible constituent in a first stage in a way known per se. In a second stage, a small-fragment fraction is initially separated from the non-combustible constituent and, subsequently, a carbon-containing light fraction remaining in the small-fragment fraction is separated.
The invention is based on the essential idea that a two-stage separation of the carbon-containing constituents is necessary for effective separation, since the proportion of carbon in the non-combustible constituent is still relatively high after separation in the first stage. The invention, moreover, proceeds from the consideration that the carbon-containing light fraction is located, above all, in the small-fragment fraction of the non-combustible constituent. The separation of the small-fragment fraction and the subsequent separation of the light fraction ensure essentially complete and reliable separation of the carbon-containing constituents from the residue.
The small-fragment fraction is preferably an inert fraction of the residue, since there is a high proportion of carbon-containing particles in the inert fraction. An appropriate plant for separating such an inert fraction is described in German Patent Application 198 22 991.7, titled xe2x80x9cPlant For The Treatment Of Solidsxe2x80x9d.
The small-fragment fraction often has, in addition to inerts and the carbon-containing particles, other impurities, in particular in the form of small wires, wire pellets or wire fibers. These may have an extremely disruptive influence in the separation of the light carbon-containing fraction from the heavier fraction of inerts and may impede the continuous and fault-free processing of the small-fragment fraction. Consequently, according to a preferred embodiment, the third device, in which the separation of the carbon-containing constituents from the small-fragment fraction is carried out, contains a facility for separating the wire-like constituents and a heavy-fragment separator, which follows this facility, for separating the carbon-containing solids.
The facility for separating the wire-like constituents advantageously ensures that wire-like constituents, which could cause disruption in the operation of the heavy-fragment separator, are not fed to the latter.
Preferably, the heavy-fragment separator has a housing, through which air is capable of flowing and in which is disposed essentially transversely to the direction of flow a grid, at the opposite ends of which are provided a first outlet for the light fraction and a second outlet for a heavy fraction. Preferably the grid is inclined relative to the horizontal.
In the heavy-fragment separator, air is blown through the grid from below, so that the fed solids are suspended above the grid. In this case, the light fraction is suspended above the heavy fraction, that is to say is separated from the latter.
An alternative method to so-called dry separation by use of an airflow is sink/float separation, in which the light fraction floats in a liquid medium and in which the heavy fraction sinks. A disadvantage of this is that a sludge is obtained, which has to be dried, and that the liquid has to be purified. In the case of the heavy-fragment separator illustrated, through which air flows and which is based on dry separation, post treatment of the separated fractions is advantageously dispensed with.
In order to maintain the operation capacity of the heavy-fraction separator, the previous separation of the wire-like constituents is critically important, since these may catch in the grid and would therefore clog the grid orifices.
For the automatic separation of the light fraction from the heavy fraction, the grid is inclined relative to the horizontal, so that the light fraction slides to the lower end of the grid, whereas the heavy fraction travels to the higher end.
The facility for the separation of wire contains, in an advantageous embodiment, a wire separator having a drum which is rotatable about its longitudinal axis and on the inner wall of which drivers are disposed and in the interior of which is provided a discharge device extending in the direction of the longitudinal axis.
Due to the drivers, in particular wire pellets are separated from the remaining solid fragments and raised in an advantageous way. At the upper reversal point, the wire pellets fall down from the drivers due to their own weight and pass on to the discharge device, by which they are removed.
Preferably, the discharge device has a vibrating conveyor that is followed by a screen, so that, by the vibrating movement of the vibrating conveyor, fine solids adhering to the wire pellets are first released from these and are subsequently separated by the screen.
In this case, the screen preferably contains lamellae that overlap in the conveying direction, there being formed between two overlapping lamellae a preferably obliquely extending gap, through which the separated small solid fragments can fall, whereas the pellets slide over the lamellae.
In an advantageous configuration, the facility for the separation of wire has a screening device for the elongate wire-like constituents, which preferably follows the wire separator. The screening device serves for the separation of elongate small wire pieces, such as, for example, small conductor wires or wire fibers, which are still contained in the solids. Preferably, the screening device contains a vibrating floor with a number of longitudinal grooves extending in the conveying direction. These are followed by screening orifices for the separation of the elongate solid fragments, the groove depth of the longitudinal grooves decreasing in the conveying direction.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a plant for the processing of residue from a thermal waste disposal plant, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.